T2 Thermocouple Spooled Wire (Ni95-(Al+Mn+Si)5)

T2 wire is bare Alumel — a nickel alloy with approximately 95% nickel and the remainder composed of aluminum, manganese, and silicon. It is the negative leg (−) in Type K thermocouples (Chromel vs. Alumel), covering −200 °C to 1,260 °C in oxidizing atmospheres. Type K is the most widely used industrial thermocouple type across a broad range of applications, and T2 (Alumel) is the negative leg that makes up the pair alongside T1 (Chromel).

Type K thermocouples operate from −200 °C to 1,260 °C in oxidizing atmospheres. T2/Alumel is not suited to reducing or sulphurous atmospheres, where selective oxidation of the aluminum content causes accelerated drift. Above approximately 1,050 °C in air, there is also a risk of green rot — preferential oxidation of the chromium in T1 that can occur when Type K thermocouples are used in low-oxygen environments near the high end of the range. Type K should not be used in these conditions; Type N or noble-metal types are more appropriate for sustained high-temperature oxidizing service.

T2/Alumel exhibits slight ferromagnetic behavior below approximately 160 °C (its Curie temperature), which can introduce small errors in thermoelectric output measurements in strong magnetic fields at low temperatures. Above the Curie temperature it is paramagnetic. This is relevant in MRI-adjacent or high-field magnetic environments, and in cryogenic thermocouple calibration where small corrections may be needed. Type E thermocouples (using T1/Chromel and Constantan) are non-magnetic and may be preferred in magnetically sensitive applications.

T2/Alumel has a higher electrical resistivity than T1/Chromel. In thermocouple construction, the leg with higher resistivity (T2) limits the current that can flow through the circuit, which is relevant when designing thermocouple amplifier circuits and extension leads. For most standard applications this is handled by standard thermocouple signal conditioning; it becomes significant only in very long thermocouple runs or in circuits with tight impedance requirements.

Bare T2 spooled wire is the raw Alumel alloy without insulation, suited to mineral-insulated thermocouple manufacture, ceramic-sleeved probe assemblies, custom winding, and vacuum-baked systems where the insulation is applied separately or provided by the mineral-insulated sheath. Insulated T2 wire — available with polyimide or polyester insulation — is a ready-to-use lead wire for thermocouple assemblies where electrical isolation between the legs is required from the wire itself.

Order T2 (Ni95/Al-Mn-Si, Alumel) as the negative leg alongside T1 (Ni90/Cr10, Chromel) as the positive leg. Both legs should be the same diameter and temper (annealed is recommended for thermocouple service). The hot junction is formed by welding the tips of T1 and T2 together. Both legs should be clearly identified — T1 is typically marked as the positive (+) leg — to ensure correct polarity in the measurement circuit.

Annealed temper is recommended for thermocouple use, providing the most consistent thermoelectric properties and ductility for junction fabrication. As drawn wire is available for applications requiring higher mechanical strength. Wire in tempers other than annealed should be annealed by the customer before use in thermocouple service.

T2 Thermocouple Alloy Spooled Wire is available in a range of diameters and lengths. Diameter tolerance is ±10% and length tolerance is +5% / −1%. For custom configurations, please contact us.